A number of fuel systems of the type in which water is supplied to the combustion spaces of engines are known. For example, systems are known in which separate fuel and water injectors are associated with each combustion space. In a further known arrangement, water and fuel are supplied, independently, to a common injector used to deliver the fuel and the water to an engine combustion space.
Where the fuel and water are supplied to the injector separately, the water is typically supplied using a remote low pressure pump, the water flowing to the injector when the pressure within the injector is low. In such an arrangement, the timing of water supply to the injector and the quantity of water supplied are not controlled accurately. Where the pump is located remotely, if a water metering facility is provided, the large volume of pressurized water may result in the quantity of water delivered to the injector being difficult to control accurately.